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This is a link post Dropping a slinky in slo-mo reveals the bottom doesn't fall until the top catches up with it.
Not the best description, but worth a watch.
(, Sat 17 Nov 2012, 18:33, Reply)
This is a normal post you see
life enriched by this.. excellent stuff - Tim and Eric below....not quite so.
(, Sat 17 Nov 2012, 18:51, Reply)
This is a normal post Witchcraft!!!!!!!!!

(, Sat 17 Nov 2012, 20:22, Reply)
This is a normal post I love that very much.

(, Sat 17 Nov 2012, 21:57, Reply)
This is a normal post I also like the phrase 'A lot of people on the internet are uncomfortable with the word "information"'.

(, Sat 17 Nov 2012, 22:02, Reply)
This is a normal post nice phrase
but I don't really buy it as an explanation.

Seems to me that when the slinky is at equilibrium, the elastic forces pulling up are in balance with the gravitational forces pulling down on the slinky. When you release the top, the slinky starts to contract as it falls (due to the elastic forces)

As the slinky shortens, the center of mass moves (and indeed drops as shown in his simulation) but because the elastic force = gravitational force - the rate of shortening (ie the bottom moving upwards) is approximately the same as the rate at which the center of mass falls.

This means that the bottom of the slinky stays where it is (at least until the center of mass catches up with it)

Where's beev when we need him?
(, Sat 17 Nov 2012, 22:45, Reply)
This is a normal post Does Hooke's Law have any place in this?
My thoughts are along the lines you've described, but I can't help wondering about the different size slinkies (so different mass and spring tension) but obviously gravity remains constant. A conundrum indeed.
(, Sat 17 Nov 2012, 22:51, Reply)
This is a normal post Or....GOD DID IT.

(, Sat 17 Nov 2012, 23:03, Reply)
This is a normal post USA! USA! USA!

(, Sun 18 Nov 2012, 0:10, Reply)
This is a normal post yes - see below

(, Sat 17 Nov 2012, 23:41, Reply)
This is a normal post this
is precisely what I was thinking while watching that.
(, Sun 18 Nov 2012, 0:43, Reply)
This is a normal post
There are multiple ways of understanding this.
You can go all the way up to a quantum mechanical model of every atom, consider it as multiple spring-mass pairs connected together, or ...

None of these are really wrong.
The shockwave propagating along the slinky is information.
(, Sun 18 Nov 2012, 2:52, Reply)
This is a normal post Hmm, but
If that were the case, wouldn't you see all the coils contracting at the same rate, not just from the top down?

I'm thinking that the changes in force take a while to ripple through the structure, With the very loose structure of a slinky, probably the optimal slinky spring, happens to also have a slower speed of force propagation to the speeds it's accelerating to.

Now if only I could write that in a way that makes sense...
(, Sun 18 Nov 2012, 14:00, Reply)
This is a normal post Yada yada physics
Centre of mass is key here.
(, Sat 17 Nov 2012, 23:40, Reply)